Power hand tool with a gearbox casing with sealing washer

ABSTRACT

A power hand tool has a gear box casing having an opening, at least one high speed shaft extending through the opening, sealing member for sealing the gear box casing against lubricant leakage. The sealing member includes a sealing washer which does not rotate and sits tightly on the shaft and which radially touches a circumference of the opening. The sealing washer is composed of an elastic material which can absorb and release lubricant.

BACKGROUND OF THE INVENTION

The invention relates to a power hand tool of the type employing sealingwashers at the output and drive shafts.

An electric tool of this type is well known from GM 79 31 401. Itsgearbox casing walls are equipped with openings which are penetrated byoutput and drive shafts, and which are sealed against lubricant leakageby means of axial seals.

In comparison with solutions employed up to now, the use of these axialseals achieves better sealing results, but also leads to a considerableincrease in the cost of the machine. The cause of this is that it isexpensive to produce the necessary low surface roughness of the counterslide way of the axial seals, and their higher cost in comparison withthe sealing washers used before.

SUMMARY OF THE INVENTION

The object of the invention is to provide a power hand tool in contrastto the conventional power hand tools, that can be more effectivelysealed without change or with very little change to expenditure onmanufacture and the costs of the individual parts, using, for example,felt sealing washers which have been normally used up to now. The sealhas a longer life than the well known axial seals. By this means,lubricants with a lower viscosity than those usable up to this time canbe used for the power hand tool of this invention.

This increases the life of the gears and the motors. Moreover, therequirement for driving energy is lower. The efficiency of power handtools in accordance with this invention, extremely important forbattery-powered models, increases markedly. Additional features of theinvention include the sealing washer being bonded with the hub, or thehub which consists of liquefiable synthetics being diffused into thissealing washer, starting at the inner circumference of the ring-shapedsealing washer. The advantage of it is that forces applied to thesealing surfaces of the sealing washer can neither push the hub andsealing washer against one another nor separate them from one another.Also the press fit of the hub, and thus the sealing washer, on the shaftis very secure.

The present invention both as to its construction and to its mode ofoperation, together with additional objects and advantages thereof, willbe best understood from the following detailed description of preferredembodiments when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-section of a power hand tool having asealing washer constructed in accordance with a first embodiment of theinvention;

FIG. 2 shoes a cross-section of the sealing washer in FIG. 1.

FIG. 3 shows a cross-section of a second embodiment of the sealingwasher according to the invention; and

FIG. 4 shows a cross-section of a third embodiment of the sealing washeraccording to the invention

DETAILED DESCRIPTION OF THE DRAWINGS

The power hand tool 1 shown in FIG. 1 shows a gearbox casing 3 mountedon a motor casing 2. The motor casing 2 encloses a motor compartment 4.In this, an electric motor with a rotor 5, not described in furtherdetail here, is fitted. Its shaft 6 drives, for example, via an angulargear not described in further detail here, a second shaft 7 serving as atool spindle. One end of the shaft 6 projects through a first shaftopening 8 into the gearbox casing 3.

The first shaft opening 8 is closed by a sealing washer 9 which sits onthe shaft 6 and turns with it. An unwanted leakage of lubricant from thegearbox casing 3 into the motor compartment 4 is thus prevented.

For the second shaft 7, there is a second shaft opening 10 on thegearbox casing, on the gear side, which leads outside. This is sealed bymeans of a second, ring-shaped sealing washer 11, so that thepenetration of lubricant along the second shaft 7 to the outside isprevented.

The detail from FIG. 1 represented in FIG. 2 shows the sealing washer 9between the gearbox casing 3 and motor compartment 4 sitting hub-like,in the form of a punched disk, directly on the shaft 6. Thecircumference of the sealing washer 9 touches the circumference of thefirst shaft opening 8, which is put in the gearbox casing 3 in the formof a cylindrical drilled hole. This shaft opening 8 is equipped with arecirculating helical groove 12 which, like the direction of rotation ofthe shaft 6, runs rising into the interior of the gearbox casing 3.

When the power hand tool 1 is operated, the lubricant filling thegearbox casing 3 will collect at the first shaft opening 8 or the secondshaft opening 10, depending on its position. Due to the sealing washer 9which rotates together with the shaft 6, the lubricant is constantlyspun outwards in a radial direction. As a result of the pump actionbetween sealing washer 9 and the corresponding recirculating helicalgroove 12, the lubricant is transported into the interior of the gearboxcasing 3.

For the power hand tool 1, both static and dynamic sealing of the firstand second shaft openings 8 and 10 is ensured. When the motor is idle,the contact pressure of the sealing washers 9 and 11 on thecircumferences of the first and second shaft openings 8 and 10 issufficient to ensure that lubricant leakage is prevented.

The second embodiment shown in FIG. 3 shows a sealing washer 29 whichsits on a hub 20 and which is secured axially by means of a thrust ring21. The hub 20 sits, rotation-resistant, on the shaft 26. The thrustring 21 which is pressed axially against the sealing washer 29simultaneously ensures that this does not rotate with the hub 20 or theshaft 6. The sealing washer 29 lies radially adjacent to the edge of theshaft exit 28 of the gearbox casing, and simultaneously touches thethreads of the recirculating helical groove 32. For axial security,there can also be an adhesive connection between the sealing washer 29and the hub 20.

The third embodiment in accordance with FIG. 4 shows a sealing washer 49in the form of a ring-shaped brush, with bristles 50 standing radiallyfree outwards. These bristles sit on a ring-shaped hub 40, and the hubis secured against rotation and sits tight on a shaft 46. With theirradial, outer area, the bristles 50 touch the edge of a conical shaftopening 48, in which a recirculating helical groove 52 is inserted. Whenthe shaft 46 rotates, the bristles 50 run in the recirculating helicalgroove 52, and constantly transport the lubricant away from the shaftopening 48 and back into the interior of the gearbox casing 43.

In the case of one design example of the invention not shown here, thehub of the sealing washer is a synthetic ring, e.g. of polyamide. It issprayed in liquid form onto the inner surface of the sealing washerwhich consists of felt or textile or similarly porous material, in thearea of the intended seating, and is ready-shaped by diffusing into it.

Felt sealing washers with external seating, which normally sit,non-rotating, in a drilled hole and through which a shaft is led, canalso be manufactured by the method described above with a syntheticouter ring.

For all the embodiments, there is a further, favorable variant if screwthread-like grooves are worked into the surface areas of the sealingwashers 9, 11, 29 and 49, and if necessary one does withoutrecirculating helical grooves 12, 32 and 52 in the shaft openings 8, 10,28 and 48, i.e. if these are smooth, cylindrical or conical drilledholes.

In addition the aforementioned sealing washers 9, 11 and 29 can have alubricant-proof impregnation on the side facing away from the lubricant.

While the invention has been illustrated and described as embodied in apower hand tool with a gearbox casing with sealing washer, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to beprotected by Letters Patent isset forth in the appended claims.
 1. A power hand tool, comprising agear box casing having an opening; at least one high speed shaftextending through said opening; sealing means for sealing said gear boxcasing against lubricant leakage, said sealing means including a sealingwasher which sits tightly and non-rotatably on said shaft and whichradially touches a circumference of said opening, said sealing washerbeing composed of a material which can absorb and release lubricant. 2.The power hand tool as defined in claim 1, wherein said sealing washeris tire-like.
 3. A power hand tool, comprising a gear box casing havingan opening; at least one high speed shaft extending through saidopening; sealing means for sealing said gear box casing againstlubricant leakage, said sealing means including a sealing washer whichsits tightly and non-rotatably on said shaft and which radially touchesa circumference of said opening, said sealing washer being composed of amaterial which can absorb and release lubricant, said sealing washerbeing formed as ring-shaped brush.
 4. A power hand tool, comprising agear box casing having an opening; at least one high speed shaftextending through said opening; sealing means for sealing said gear boxcasing against lubricating leakage, said sealing means including asealing washer which sits tightly and non-rotatably on said shaft andwhich radially touches a circumference of said opening, said sealingwasher being composed of a material which can absorb and releaselubricant, said sealing washer having one side facing away from saidgear box casing and being impermeable on said one side, said sealingwasher having another side which is opposite to said one side and beingpermeable on said another side.
 5. A power hand tool, comprising a gearbox casing having an opening; at least one high speed shaft extendingthrough said opening; sealing means for sealing said gear box casingagainst lubricant leakage, said sealing means including a sealing washerwhich sits tightly and non-rotatably on said shaft and which radiallytouches a circumference of said opening, said sealing washer beingcomposed of a material which can absorb and release lubricant; and a hubwhich sits tightly on said shaft, said sealing washer fitting tightly onsaid hub.
 6. A power hand tool, comprising a gear box casing having anopening; at least one high speed shaft extending through said opening;sealing means for sealing said gear box casing against lubricantleakage, said sealing means including a sealing washer which sitstightly and non-rotatably on said shaft and which radially touches acircumference of said opening, said sealing washer being composed of amaterial which can absorb and release lubricant; a hub and sits tightlyand non-rotatably on said shaft, said sealing washer being fixed axiallyon said hub and secured against rotation; and a retaining disc by meansof which said sealing washer sits axially on said hub.
 7. A power handtool, comprising a gear box casing having an opening; at least one highspeed shafts extending through said opening; sealing means for sealingsaid gear box casing against lubricant leakage, said sealing meansincluding a sealing washer which sits tightly and non-rotatably on saidshaft and which radially touches a circumference of said opening, saidsealing washer being composed of a material which can absorb and releaselubricant, said opening being provided with screw thread-likerecirculating helical grooves which lead into an interior of said gearbox casing.
 8. The power hand tool as defined in claim 7, wherein saidrecirculating helical grooves are provided in an area in which saidsealing washer is in contact with said opening.
 9. A power hand tool,comprising a gear box casing having an opening; at least one high speedshaft extending through said opening; sealing means for sealing saidgear box casing against lubricant leakage, said sealing means includinga sealing washer which sits tightly and non-rotatably on said shaft andwhich radially touche a circumference of said opening, said sealingwasher being composed of a material which can absorb and releaselubricant, said sealing washer having an outer radial circumferentialarea and being provided with helical grooves on said outer radialcircumferential area.
 10. A power hand tool, comprising a gear boxcasing having an opening; at least one high speed shaft extendingthrough said opening; sealing means for sealing said gear box casingagainst lubricant leakage, said sealing means including a sealing washerwhich sits tightly and non-rotatably on said shaft and which radiallytouches a circumference of said opening, said sealing washer beingcomposed of a material which can absorb and release lubricant; and a hubwhich is fitted on said shaft, said sealing washer is bonded with saidhub.
 11. A power hand tool, comprising a gear box casing having anopening; at least one high speed shaft extending through said opening;sealing means for sealing said gear box casing against lubricantleakage, said sealing means including a sealing washer which sitstightly and non-rotatably on said shaft and which radially touches acircumference of said opening, said sealing washer being composed of amaterial which can absorb and release lubricant; and a hub fitted onsaid shaft, said hub being composed of liquefiable synthetic materialwhich is diffused into said sealing washer starting at an innercircumference of said sealing washer.
 12. A power hand tool, comprisinga gear box casing having an opening; at least one high speed shaftextending through said opening; sealing means for sealing said gear boxcasing against lubricant leakage, said sealing means including a sealingwasher which sits tightly and non-rotatably on said shaft and whichradially touches a circumference on said opening, said sealing washerbeing composed of a material which can absorb and release lubricant,said sealing washer having an inner circumference which is sprayed witha synthetic material.
 13. A power hand tool, comprising a gear boxcasing having an opening; at least one high speed shaft extendingthrough said opening; sealing means for sealing said gear box casingagainst lubricant leakage, said sealing means including a sealing washerwhich sits tightly and non-rotatably on said shaft and which radiallytouches a circumference of said opening, said sealing washer beingcomposed of a material which can absorb and release lubricant, saidsealing washer having a radial inner surface which is coated with aliquefiable, self-hardening synthetic material.
 14. A power hand tool,comprising a gear box casing having an opening; at least one high speedshaft extending through said opening sealing means for sealing said gearbox casing against low viscosity lubricant leakage, said sealing meansincluding a sealing washer which sits tightly and non-rotatably on saidshaft and which radially touches a circumference of said opening, saidsealing washer being composed of a porous material which can absorb andrelease a low viscosity lubricant, said washer having an innercircumference with a region in which a liquefiable, consolidated plasticis concentrated so that a hub is formed as a non-detachable part of saidwasher, said opening being provided with a return helical groovesdirected into an interior of said gear box housing.